Tape‐Free, Digital Wearable Band for Exercise Sweat Rate Monitoring

Abstract

lying physical conditions that current devices may be unable to access. [3,[8][9][10] For example, sweat rate is important for the assessment and diagnosis of physical conditions like hyperhidrosis (excessive sweating) and hypohidrosis (lack of sweating) during sedentary or daily activities; it can also be used along with fluid intake quantities to assess the dehydration levels of athletes to maintain proper fluid balance and bodily functions. [11][12][13][14][15] Moreover, monitoring the rate of sweat production enables further analyses, as different sweat rates modulate the concentration of secreted analytes and are thus of critical importance for interpreting analyte concentration measurements. [16][17][18][19] Even though monitoring sweat rate has been studied tremendously in the past few years, only a few devices have become commercially available. [20,21] In addition, most of the new concepts are yet to be accepted by the medical field for consistent reliable health monitoring due to the requirements of safe and biocompatible build materials, comfortable geometry and form factor, and accessible and consistent mass production. [22][23][24] Traditional methods for monitoring sweat rate such as whole-body washdown and gravimetric pads are done off-body, in specialized settings, and with the intervention of trained Monitoring sweat secretion rate is essential for uncovering underlying physical conditions like hyperhidrosis, mental stress, and neural disorders. Often, flexible microfluidic sweat rate monitoring devices use tape as a means of attachment to the skin to tightly seal the collection area. While these single-use, adhesive-backed devices have lightweight and thin interfaces for mounting on the skin, their form factor complicates their potential integration with available commercial wearables, such as smartwatches. Here, a tape-free device, consisting of a 3D-printed sweat collector with a concave surface that is strapped onto the skin to form an effective seal, is presented. The materials, structure, and dimensions of the sweat collector are optimized for conformal device-to-skin contact and efficient capture of sweat. The collector is interfaced with a fluidic microchannel with embedded electrodes for continuous digital monitoring of sweat rate. Long-term exercise-induced local sweat rate from multiple body locations in both multi-subject and longitudinal studies is measured, depicting the correlation between the measured sweat profile and total body fluid loss. The simple installation procedure and reusability of this tape-free device make it a good candidate for integration with the band of a watch.

Wearable Humidity Sensor for Continuous Sweat Rate Monitoring

“…[ 34 ] In addition, the sweat collector's performance on the forearm yielded consistent and reliable results during on‐body trials in our previous work. [ 22 ]…”

“…With these considerations in mind, the sweat collector's surface area was set to 1.14 cm 2 with a curvature depth of 2 mm, which proved to be watertight and comfortable for this study's experiments, consistent with our prior publication's empirical testing of these qualities. [ 22 ]…”

“…A detailed description of the fabrication process of the collection well was included in a previous study. [ 22 ] In brief, the two components were 3D‐printed together. The collection well was 3D‐printed in Agilus30 Clear, a PolyJet photopolymer that was tear‐resistant and flexible.…”

“…The materials used to fabricate the device proved to be sturdy and durable, which was more extensively tested in the prior work that conceived the sweat collector. [ 22 ]…”

“…In our previous work, we developed a tape‐free device that uses impedimetric measurements to calculate a user's continuous sweat rate during exercise periods. [ 22 ] While larger‐scale studies have yet to be conducted with this form‐factor, these device designs present promising opportunities for integration with existing smartwatch bands…”